In a test tube containing a salt, a few drops of dilute H2SO4 was added, which gave colourless vapours having the smell of vinegar. The vapours turned the blue litmus paper red. Identify the correct anion from the following :
- Carbonate, CO32-
- Sulphide, S2-
- Acetate, CH3COO-
- Sulphate, SO42-
Answer
(3) Acetate, CH3COO-
Solution
Dilute H2SO4 liberates the volatile acid of the anion:
2CH3COO- + H2SO4 2CH3COOH + SO42-
Acetic acid vapours are colourless, smell of vinegar and are acidic (turn blue litmus red).
(Carbonate gives odourless CO2, sulphide gives H2S with rotten egg smell, sulphate gives no gas with dil. H2SO4.)
∴ The anion is acetate.
Answer: (3)